Build usb-ohci for PCs

The OHCI emulation isn't obviously broken and there are people who want to use
it. Let's build it by default so that it can be enabled via -device.

Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Signed-off-by: Aurelien Jarno <aurelien@aurel32.net>
diff --git a/default-configs/x86_64-softmmu.mak b/default-configs/x86_64-softmmu.mak
index ec98af2..e0f7fc0 100644
--- a/default-configs/x86_64-softmmu.mak
+++ b/default-configs/x86_64-softmmu.mak
@@ -1 +1,3 @@
 # Default configuration for x86_64-softmmu
+
+CONFIG_USB_OHCI=y